A heat recovery device that recovers exhaust heat from thermal components is, for example, described in JP-B2-8-6608 corresponding to U.S. Pat. No. 5,127,470. In the described heat recovery device, a reaction material in a first chemical heat accumulator is heated by high-temperature exhaust gas exhausted from thermal components to discharge reacted material, and a gas obtained as the result of heating the reaction material is subjected to heat recovery at a heat exchanger. Thereafter, a reacted material in a second chemical heat accumulator is heated and vaporized to cause reaction with a reaction material in the second chemical heat accumulator. Further, output is extracted by passing water through a container holding the reacted material in the first chemical heat accumulator and further passing it through a container holding the reaction material in the second chemical heat accumulator to produce high-temperature vapor.
In the described heat recovery device, it is possible to appropriately extract the output according to demand. Further, it is possible to obtain vapor having the temperature higher than the temperature of the exhaust gas from the thermal components.
However, a certain amount or more of exhaust heat (external heat) obtained from a heat engine needs to constantly exist to appropriately extract output according to demand. For this reason, if such a heat recovery device is employed to a system involving such an amount-of-heat fluctuation that the amount of heat obtained from a heat engine is reduced with time, there is a possibility that the reaction material in the first chemical heat accumulator cannot discharge the reacted material because of an insufficient amount of heat. Therefore, when the described heat recovery device is employed to a system utilizing exhaust heat from thermal components involving an amount-of-heat fluctuation, a problem that heat recovery operation is not established may arise.